Technical Field
The present invention concerns a method of controlling a wind power installation and a corresponding wind power installation.
Description of the Related Art
Wind power installations are generally known and serve to take kinetic energy from the wind and convert it into electric energy to feed that into an electric network. In that respect, wind power installations nowadays also perform the task of supporting the electric network into which they feed.
Thus for example German patent application DE 100 22 974 A1 from the year 2000 (application filed on 22 Nov. 2001) describes frequency-dependent power regulation. In accordance therewith it is proposed that, with a rising network frequency, the power which the wind power installation feeds into the network is reduced as soon as the network frequency has exceeded a limit value.
That takes account of a network situation in which there is a surplus of energy supply, which because of the performance of large power stations, leads to a frequency increase which the invention in accordance with the above-mentioned application DE 100 22 974 A1 addresses.
In the case of an insufficient supply of energy or an increased energy requirement in the network there would be a drop in frequency to which it would ideally be possible to react with an increase in the power which is fed into the network. An increase in the power to be fed in is however difficult to implement by a wind power installation because the wind power installation optimally already feeds into the network the maximum power which can be taken from the wind. In order nonetheless to permit at least a short-term increase in power, it is proposed for example in accordance with German patent application DE 10 2009 014 012 A1 that a short-term increase in power be effected, using the rotational energy stored in the moment of inertia of the rotor generator system. Such a method however is dependent on the rotational energy stored in the rotor generator system.
As further state of the art attention is directed at this point generally to the following publications DE 103 41 502 A1, WO 2011/000531 A2 and WO 2005/025026 A1.